1. Field
The present invention relates to aircraft components. More particularly, the invention relates to a method and apparatus for manufacturing an aircraft stringer.
2. Related Art
To fabricate a composite integrated stinger and fuselage skin structure for an aircraft, vulcanized rubber hollow tubes with stiffened inserts are placed within the hollow stringer sections. Autoclave pressure keeps the stringer section from collapsing during the automatic fiber placement (AFP) and composite cure cycle. The vulcanized rubber hollow tubes, for example, are typically pressurized to provide pressure of 85 lbs/sq. in. to the composite material making up the hollow stringer section, pressing the composite material against a tooling.
The stiffened inserts can be made of a variety of materials. For example, the stiffened inserts can be made of rubber, such as a different type of rubber than used in the hollow tube. The stiffened inserts slide inside the hollow tube to reinforce the hollow tube and keep the tube from collapsing during AFP of composite material against an outer wall of the hollow tube.
Unfortunately, the rubber hollow tubes can sometimes burst, ruining the composite part. Additionally, the hollow tubes are costly and require frequent replacement, since the rubber shrinks and the tube loses its pressure integrity with each subsequent cure cycle.
Accordingly, there is a need for an apparatus and method for supporting a stringer during AFP and/or a cure cycle that overcomes the limitations of the prior art.